Compilare: user.cpp: In function ‘int main()’: user.cpp:89:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < X.size() - 1 ; ++ j) ^ user.cpp:91:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = X.size() - 1 ; j < Y.size() ; ++ j) ^ user.cpp:95:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0 ; j < Y.size(); ++ j) ^ user.cpp:98:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = Y.size() + 1 ; j < X.size() ; ++ j) ^